Rubber-metal laminated plates are conventionally used as engine cylinder head gaskets. As such a rubber-metal laminated plate, one in which a rubber composition is coated and laminated on a metal plate is used; however, when using a rubber-metal laminated plate in which the rubber surface is not subjected to any surface treatment, the wear resistance is low even at ordinary temperature. In particular, when this rubber-metal laminated plate is used as a cylinder head gasket, it may be worn out to cause leakage. In contract the present applicant has previously proposed that a fluororubber surface is coated with a surface-treating agent comprising a hydroxyl group-containing liquid polybutadiene, an isocyanate group-containing polybutadiene as a curing agent, and a polyolefin resin organic solvent dispersion (Patent Document 1). In this case, the wear resistance at ordinary temperature is excellent; however, the wear resistance tends to decrease after aging due to heat. For the application to gaskets to be used in a high temperature environment, a further improvement in the function is expected.
Patent Document 2 discloses an automotive sealing material in which a DLC (diamond-like carbon) film having wear resistance and lubricity is formed by a plasma CVD method on the surface of a substrate of the automotive sealing material on which a film comprising an organic material is to be formed; however, a fluorine termination treatment or hydrogen termination treatment is required as a pretreatment before the DLC film formation. This treatment is supposed to improve the adhesion of the carbon film and the sealing material substrate.
Further, as a technique for forming a DLC film having excellent adhesion on the surface of a polymer substrate, Patent Document 3 proposes that a carbon intermediate layer film is formed between the polymer substrate and the DLC film. Comparative Example 1 shows that the DLC film is peeled off when such an intermediate layer film is not formed.